The present invention generally relates to a copying machine and more particularly, to an automatic double-side or duplex copying machine (referred to as a duplex copying machine hereinafter) capable of automatically forming images on both sides of a copy paper sheet and provided with a circulatory document feeder which is capable of circularly transporting each of a plurality of original documents placed on an original tray to an original platform. The present invention also relates to a method of treating a paper clogging i.e. a paper jamming which has taken place in reverse-side copying operation wherein a copying operation is carried out on a blank reverse side of a one-side copied paper sheet during an automatic double-side copying operation, with the automatic duplex copying machine also being intended for use in an interruption mode thereof.
A known automatic duplex copying machine is provided with a switch-back transport passage and one or more intermediate storing locations for one-side copied paper sheets between a paper discharging portion and a copying process portion, whereby each of one-side copied paper sheets is led to the switch-back transport passage so that its transporting direction is turned the other way and thereafter, each of them is temporarily stored in the intermediate storing portion. After an original on the original platform has been replaced by a next original which is to be copied on the blank reverse side of a one-side copied paper sheet, the one-side copied paper sheet in the intermediate storing portion is transported to the copying process portion so that an image is also formed on the reverse side thereof which is caused to face the surface of a photosensitive member.
Furthermore, there have conventionally been such an automatic duplex copying machine which is provided with an automatic document feeder for supplying and discharging each original to and from the original platform in order to simplify the replacing of originals during the automatic double-side copying operation, and another automatic duplex copying machine which is provided with a sorter in a paper discharging portion thereof in order to simplify the adjusting required for originals during the double-side copying operation for a plurality of originals having consecutive pages, each of which copying machines is commercially available nowadays.
In the automatic document feeder for automatically supplying and discharging mainly one-sided originals each having an image on one side thereof, there is generally known a circulatory document feeder which is capable of transporting each of a plurality of originals placed on the original tray to the original platform in the order from the lowest one, and discharging the original on the original platform onto the uppermost one of the originals placed on the original tray.
There has also been conventionally proposed a method of conducting the automatic double-side copying operation by employing the automatic duplex copying machine having the aforementioned circulatory document feeder and sorter, wherein a copying operation is carried out on each odd page of originals during the first circulation thereof in the circulatory document feeder, and each of one-side copied paper sheets according to the above described process is stored in an intermediate tray. During the following second circulation of the originals, each of one-side copied paper sheets is supplied from the intermediate tray only for the originals of even pages so that the original on the original platform is copied on the blank reverse side of a one-side copied paper sheet. According to the above described method, since only one alteration from one-side copying operation to the reverse-side copying operation is only required irrespective of the number of originals, the copying machine is desirably decreased in wear and failure thereof. In the automatic double-side copying operation, however, the paper transport passage is remarkably complicated and prolonged, and the paper is easily distorted with being heated and pressed by fixing rollers in a copying operation for one side thereof. Accordingly, in the automatic double-side copying operation, particularly, in the copying operation for the reverse side of a copy paper sheet, since failures are liable to arise in supplying or transporting the paper, a paper jamming sometimes takes place in the paper transport passage. When the paper jamming has taken place in the copying operation for one side of the copy paper sheet, the paper which is brought to a standstill in the transport passage is removed therefrom and upon release of the paper jamming, the automatic double-side copying operation can be continued by repeating the copying operation for the insufficient number of copied paper sheets. On the contrary, when the jamming has taken place in the copying operation for the reverse side of one-side copied paper sheet, it is necessary to carry out not only the copying operation for the reverse side thereof, but also the same operation for the front side thereof again.
Conventionally, there is no such automatic duplex copying machine whereby the copying operation can be easily carried out on the front side of copy paper sheet for an insufficient number of copy paper sheets in a case where the jamming has taken place in the copying operation for the reverse side of one-side copied paper sheet. In particular, in an automatic duplex copying machine whereby the one-side copied paper sheet is transported to the copying process portion in the order from the lowest one to the upper on the intermediate storing portion, it is required to carry out the double-side copying operation with respect to the original which has been subjected to the jamming, after all of the reverse-side copying operations have been completed. Therefore, in case of double-side copying operation on the originals having consecutive pages, adjustment of the copies after the copying operation becomes extremely complicated. Particularly, there have been such drawbacks that in a copying machine having a sorter thereon, its function can not be effectively utilized, and in another copying machine having a document feeder thereon, replacement of the originals becomes complicated. Furthermore, each copying machine of the above described type also has the drawback that during the double-side copying operation for a plurality of originals, since a copying operation for the other originals is not allowed to be carried out in an interruption mode, the copying machine can not treat a copying operation which is an emergency.